Safety in and around vehicles is an important issue. In particular, a big safety concern at the moment is that of a car or truck backing up. One of the most effective means for increasing safety against bodily injury due to a backing up vehicle is with the aid of a back up alert device which makes a "beep""beep" warning sound while the truck is in reverse motion--thus warning any persons behind the vehicle.
Current back-up alarms on the market need to be physically mounted to the vehicle (usually with a bolt or two) and then electrically hooked into the back-up light wire. Thus when the vehicle is in reverse--and power is going to the back-up light--power will now power up the back-up alarm. This installation is very awkward and time consuming.
Ninety-five percent of all such vehicles use a standard 1156 back-up light which plugs into a socket at the rear of the car. There is a more specialized market for trucks which uses a slightly different back-up light than the 1156 bulb mentioned above. This light is a 4" diameter assembly forming a housing which contains a bulb (similar to the 1156) within.
This 4" back-up light has a clear lens and an opaque white back which acts as a reflecting surface of the bulb which is mounted in the center of the housing by a mechanical shock-absorbing mount which in turn has two wires which are mechanically connected to two electrical plugs which are also part of the housing. The whole assembly is hermetically sealed--thus acting as one unit. The unit fits (with the aid of a grommet) into a 4" hole at the rear of the vehicle and hooks into a 2 wire electrical connector which will supply it with power.